DESCRIPTION (applicant's description): The goal of the proposed research is to characterize protein interactions that are important for eukaryotic translation initiation. The research will be focused around eIF4G, which is of central importance for the recruitment of the ribosome to mRNA. eIF4G interacts with a number of other proteins or protein complexes, such as eIF4E eIF3, eIF4A, Mnkl kinase and Poly(A)-binding protein, as well as with RNA. These interactions are important switches for regulation of protein expression, and the proteins involved are targets of signaling pathways and regulatory binding proteins. Furthermore, they are targets of cellular and viral proteases. The regulatory processes include phosphorylation of eIF4G and eIF4E or the cleavage of eIF4G during apoptosis and in picornavirus, infection. eIF4G is a multi-domain protein with subunits of yet unknown structure. It may only be partially folded, and its functional domains may undergo a folding process upon binding its target molecules. Considering the importance of this system, we propose research towards the following topics: 1. The structure of the ternary complex of yeast eIF4E m7Gpp and yeast eIF4GI393-490. 2. The structure of the ternary complex of human eIF4E m7Gpp and a minimal 4E-binding domain of a human eIF4G. 3. Analysis of the mutual interactions between e1F4E, cap analogues and eIF4G. 4. Regulation of the eIF4E/eIF4G interaction by 4EBP. 5. Domain organization of the entire eIF4G, can we correctly predict domain boundaries and express individual domains? Are these putative domains folded and suitable for structural studies? Can we characterize structures of other domains of eIF4G and study interactions with other proteins?